In recent years, print on demand (POD) book printing, binding and trimming systems (POD book publishing systems) have been developed, such as shown in my U.S. Pat. No. 7,014,182. This last-mentioned patent used one or more conventional black and white duplex laser printers for printing the text pages that constituted the book block of the POD book. A color cover for such POD books was also conventionally printed by a cover printer was married to the book block to form a perfect bound book. In recent years, advances have been made in color printers such that those skilled in the art will recognize that such modern color printers can economically used to print the text pages of a POD either in black and white, or in color.
While such print on demand book printing, binding and trimming apparatus, as described in my above-noted U.S. Pat. No. 7,014,182, worked well, it was found that certain problems arose in adhesively binding the cover to the spine of the book block. The amount of the adhesive applied to the spine of the book block was the same for thin book blocks and for thick book blocks. On thinner book blocks, excess adhesive was oftentimes applied to the spine such that when the cover was bound to the spine, such excess adhesive was forced from between the spine and the inside of the cover in contact with the spine and this excess adhesive flowed onto the face of the book block proximate the spine and onto the inside faces of the cover proximate the spine. While some such excess adhesive may be desirable because it held the cover in a flat condition against the outer pages of the book block, if too much adhesive was present between the cover and the face of the book block proximate the spine, this excess adhesive would form a ridge in the cover giving the book a pronounced “widow mark” (i.e., an indentation and a corresponding ridge formed on the cover along the spine) when the binding clamp gripped the cover and the book block adjacent the spine. While such books were still usable, they gave the book an appearance deficiency and made it difficult for the book to remain in an open position. Still further, such excess adhesive may form a pronounced ridge that cause the cover to bulge adjacent the spine and this may result in a book perceived to be of inferior quality.
As shown in FIGS. 1 and 2 of my above-noted U.S. Pat. No. 7,014,182, an adhesive application station AS was provided along the workpath WP. The adhesive application station had a rotary adhesive application wheel or drum that was at least partially immersed in a bath of hot melt adhesive that was heated to a desired application temperature (e.g., about 350-400° F., depending on the characteristics of the particular adhesive being used) sufficient to liquefy the hot melt adhesive. The wheel was rotatably driven about a horizontal axis generally perpendicular to the direction of relative movement between the book block and the wheel. As the wheel rotated up out of the bath of the liquefied adhesive, the peripheral edge of the wheel picked up a quantity of the adhesive thereon. The bottom edge of the spine was positioned so as to have an operatively relationship with the upper peripheral surface of the wheel (i.e., to be clear of the wheel but to be in contact with the layer of adhesive on the wheel) as the book block moved relative to the wheel so that a coating of the adhesive was applied across the width of the spine and along the length of the spine. However, the amount of adhesive carried by the wheel and applied to the spine could not be controlled and thus the same amount (thickness) of adhesive was applied to the spine, regardless of the thickness (width) of the spine. Counterintuitively, this has been found to result in excess adhesive being applied to thicker book blocks and insufficient adhesive applied to thinner book blocks.